Stylus



June 1, 1948. w, G, H, FINCH 2,442,561

STYLUS Filed Feb. 2, 1944 INVENTOR ATTORN EY.

Patented June 1, 1948 UNITED STATES PATENT OFFICE n STYLUS William G. H. Finch, Newtown, Conn.

Application February 2, 1944, Serial No. 520,733

2 Claims. (Cl. 234-70) My invention relates in general to picture transi mission systems and more particularly concerns a novel means for recording facsimile images upon a dry conductive record sheet.

In facsimile transmission systems, a transmitting-scanning member is operative to genera-te electrical currents which fluctuate in accordance with the lights and shades of elemental areas of an image to be transmitted. These currents are amplified and are transmitted by Wire or radio to a remotely disposed recording unit. The recording process generally comprises the operation of a stylus across a record sheet in a manner which duplicates the motion of the scanning member at the transmitter.

In one form of facsimile recording system, the recording shee't is paper or similar material rendered conductive by impregnation with a suitable metallic element such as finely divided carbon or finely divided aluminum.

One surface of this conductive sheet is chemically sensitized by a material such as titanium oxide which discolors upon the passage of an electrical current therethrough. The recording Vsheet is mounted upon a conductive platen and is traversed by a conductive stylus in contact therewith.

. The incoming facsimile signals are impressed `between the surfaces of the conductive sheet by Y `dryrecording has been accompanied by various disadvantages which have often marred the tldelity of the reproduction to a point where the image was unrecognizable.

The disadvantages resulting from `the use of dry recording paper in conjunction with a, recording stylus have been in part a result of con- 'ductive stylus utilized to traverse the recording sheet. Generally, the stylus utilized assumed the lform of a'needlelike metallic member biased fagainst the conductive paper. '.I'he area'of con. Ytact between the end of the stylus and the surface of the recording sheet was necessarily of the order of the area covered by a scanning mem ber at the transmitter.

Sinceethe transmitting scanning member normally comprised a light beam focussed to a spot upon the surface of the image, this scanning spot was of relatively small diameter and normally less than 1/100 of an inch. Thus the recording stylus was correspondingly of the order of 1/100 of an inch in diameter so that the Width of a scanning line drawn by the recording stylus Was substantially equal to the width of the line scanned at the transmitter.

The utilization of fine diameter recording stylus Was impossible with dry recording paper of the type described, since styli having relatively sharp recording points would tend to cut into the recording sheet. Furthermore, the consideration of the mechanical strength of the stylus was important in determining the minimum diameter which could possibly be utilized.

Amongst the foremost vdisadvantages of a pointed recording stylus for traversing a conductive sheet was the accumulation of gummy conductive substance thereupon due to the aforementioned cutting eiect which the stylus exercised upon the recording sheet.

Since the recording sheet is essentially conductive throughout, the material which would tend to accumulate upon the point of the recording stylus was correspondingly conductive and'thus the effective conductive area in contact with the recording sheet would increase greatly as the recording progressed.

Consequently the final image would loe-blurred as the width of the recording trace increased due to the accumulation of conductive matter upon the stylus and the resulting pictures were at times distorted beyond recognition. l

In order to preclude the deposition of conductive material upon the stylus point which would result in an overlap of the recording traces, a wafer stylus was devised.

This recording stylus comprised a fine disk rotatably supported upon the scanning arm and having associated cleaning apparatus for remov ing any material which would tend to deposit.

The stylus would traverse the sheet 'in a rolling contacting manner, and thus by the application of a Wiper to the edge of the stylus, it

' was possible to remove accumulated material.v

A Thus, although the disk stylus could be made as thin as practical to obtain a scanning linefof extremely fine wid-th, the stylus still had to be of appreciable diameter in order to provide for the rotatable support andthe like.

Since dry conductive paper or similar material is relatively soft, the rotatable stylus would tend to cut into the paper and thus electrical contact would be made over a surface which was substantially rectangular. In other words, the stylus would contact the paper over a width equal to the Width of the stylus and over a length in the direction of the scanning movement which was a function of the depth to which the stylus would penetrate.

Thus the resolution of fine detail by means of a disk stylus has been found impossible.

Summarizing the above,V therefore, it may be" seen that prior recording styli of the conductive type for operating upon instantaneously charmaccumulation of conductive material thereupon. A further object of my invention is to provide Y for a recording stylus of extremely small recording area which will not cut or otherwise mar the surface of the recording sheet.

A still further object of my invention is to provide for a recording stylus having an exposed contacting surface of relatively small area and an insulating embedment providing mechanical strengththerefor. I

These and other objects of my invention will now be apparent from the following detailed 'speciiication takenin connection with the accom- Y panying drawings, in which:

cally treated recording paper presented two salient difficulties namely the tendency to cutinto j the paper and the tendency to smudge or blur the image as a result of the aocumulation'of the conductive material thereupon.

The present invention contemplates a needle like recording` stylus which overcomes the aforementioned disadvantages of recording styli hereinabove enumerated. The novel recording stylus of myinvention comprises essentially Ya needle like structure embeddedin an insulating compound whichserves as a support therefor.

The surface area of contactbetween the novelV conductive stylus and the` recording sheet may be made as small as is consistent with the detail which itis desired to record faithfully, while the Y accumulation of conductive material about the recording edge 'thereof is impossible.` Furthermore ,the problems heretofore experienced insofar as mechanical support for the stylus Vwas cone cerned, have been :completely overcome by the present stylus arrangement.

The needle like'sty'lus is kembedded in an insulating compound of durable characteristics and an exposed edge thereof is adjusted to be liush or coextensive with the surface of the insulating material. yThe surface of the insulating material containing the exposed edge of the recording stylus is preferably sphericalV or the like in form and of a relatively large radius of' curvatureas compared with the diameter of the stylus.

The surface'of the insulating material and the exposed edge of the stylus ar highly polished to present a VuniformV smooth contacting surface.

The entire assembly of stylus and insulating em-' bedment therefor, is then vsuitably positioned Within a scanning apparatus at the recorder and is biased to surface engagementV with therecordingsheet. e

It is obvious that during the motion of this re- Figure 1 is a diagrammatic representation of a facsimile recorder. Y

Figure 2' is a schematic representation of the Yprinciples of my novel recording stylusrand Figure 3 is a cross-'sectional view of the recording elements of a` facsimile scanner and il'- lustrates my novel recording stylus in connection therewith. Y A conventional type off facsimile recorder is illustrated in nFigure l andis adapted for the novel type of stylus which I have devised.

AsV previously mentioned, a transmitting unit having a light'beam stylus and associated photoelectriccell may generate electrical signals uctuating in accordance with'the lights and shades of pictures to be transmitted. VThese signa-ls may be caused to modulate a radio frequency carrier f `and'be transmitted thereby toV areceiver such as trated inV this embodimentis of the rotatableV drum type. As illustratedqa source of mechan ical energy such as electric motorv 26 energized from a power line through theleads 2l drives the drum 3l through a speed reducer32.

. `The motor also drives'worm 33 ,and thusasso- Y ciated worm gear 3s which imparts a rotary motion to the feed screw 35, suitablyV journalled as cording stylus across the conductive sheet that it j will be Nimpossible for the relativelyv smooth contacting surface to cut or otherwise mar the surface of the recordingsheet. Furthermore the relatively broad surface area presented by the entire stylus assembly will serve during the re-.

cording process to smooth the conductive nap of the recording sheet. which would normally tend to be dislodged and accumulate upon the stylus,

Y I have discovered that I may fabricate the stylus of as fine a diameter wire as'possible Vand provide sulcient mechanical support 4and, bracing'solely bythe insulating' embedment.`

`jItLi'S' therefore an object of my invention to provide a novel recording stylus. Y,

Another objectief any invention is to provide a facsimile recording stylusv of extremely une diameter in'an insulating embedment;

. Y' Still another object of my invention is to pro- Y vide a recordingstylus which will Dreclude'the and as which encircle tne'eyiindricai'drum K and support thepaperthereupon.

schematically illustrated. The feed screw 35 drives, by means of half-V nut 35 whichis ingengagement therewith, the recording stylus assembly Which will hereinafter be described in further detail, The pitch of the feed screw is predetermined so that the recording stylus assemblytl advances approximately 1/ioo of aninch'during each revolution Aof the drum 3 i e lf, however, it is desired to place the scanning lines closer together, the pitch of the-feed screw 35 may bedecreased accordingly. :The drum 3|` is conductive and supports arecord sheet 4| thereupon. The record sheetlnay'of course be mountedln any suitable'manner and as indicated,V the record sheet is arranged to have an'overlap at i2 and is'maintained inxed relation with the drum 3l by means Vof a pair of garteresprings 43 The drum is rotated in the direction indicated by arrow head 45'in order to preclude interference cylindrical member 66.

7 insulating compound 62.V The stylus has an exposed surface 63 similar to that illustrated in Y Figure 2 and the insulator 62 has a coextensive curved surface 64.' In the fabrication of the stylus assembly illustrated in Figure v3 or that illustrated in Figure 2, the insulating material is molded directly about the stylus in any suitable Y manner. Thus, if the insulating material is a plastic, the normal type of thermal molding mayY be'appliedcr the stylus 6l may be embedded inl molten glass or the like. The stylus is preferably distorted along its length as indicated at 6I in order that -when molded within'the insulating material, motion thereof and subsequent loosening will be impossible. However, a straightV 'section of the stylus is retained immediatelyin the vicinity of the exposed area 63.

When the molding process is complete, the surface 63 of the metallic element 6I and 66 of the insulating element 62 are ground or otherwise finished into a smooth continuous surface having a comparatively large radius'cf curvature.

This may be accomplished by 'ordinary grinding and polishing materials or is preferably accomplished in the mannerwhich 'is-well known Vfor imparting highly polished spherical surfaces to glass as in lenses. The grinding apparatus is arranged in a predetermined manner so that the end of the metallic element 6l Vis normal to the surface 64 of the insulating material.

Subsequent to the grinding and polishing operation the insulating material 62 is turned into cylindrical form and the shoulder 65 is formed therein. The stylus support as illustrated in Figure 3 comprises essentially a hollow cylindrical metallic member 66which slidably supports the insulating material 62 along the cylindrical surface 61 and has the reentrant circular an'geBS for permitting the passage of the smaller diameter section of the insulating material. The reentrant flange 68 is adapted to engage the facsimile circuit. The assemblyV is then completed as illustrated by inserting compression spring 8l into the .cylindrical member so that the spring bears against the reentrant flange 82 thereof. Y v

The pigtail lead isthen drawn through per- A shoulder 13 in theY members, the stylus assembly may-be insulatedly positioned thereupon.

The compression spring 8l provides a bias on the stylus assembly 6|-62 which drives it toi end Q2 of the member 81.

The lower end ci the member 81 carries the half nut 36, which when engaged with,` the rotating feed screw causes theV lateral'displacement of the entire stylus assembly.V

The member 81 is pivotally and slidably positioned upon a xed rod 63, andfisgnormally biassed in any convenient manner so that the' stylus assembly tends to contact the record sheet. The inward movement of the stylus holdingV arrangement is limited bythe engagementof the hali nut 36 and the feed screw 35 and by the engagement of a roller Sii and a iixed Yguide rail 95, The rolleril is'carried upon the memberl by a suitable yoke Q6.

V./-ls illustrated in ligure,Y the engagement of the roller 912 and the rail 95 is prearranged so that the'axis ofthe straight end of `the stylus 6| intersects the'aXis of the drum.

When it is desired to reset the stylus to a particular Iposition the member 81 is rotated about vthe rod 93 against its normal bias sc that the Ahalf nut 36 is disengaged. The stylus carrying member 81 may then be placed in any position, and the half nut reengaged as shown in Figure 1.

When in the operative position as illustrated in Figures 1 andV 3, there is considerable clearan-ce at 86 between the shoulder 65 and the flange ThisV clearance at S6 permits the spring 8l to determine the position of thestylus lil-V62 against the record sheet. v Y Y Further, the spring loading ofthe stylus as illustrated in Figure 3 permits the'stylus to ride easily over the overlap 42 in "the paper sheet as illustrated in Figure 3; without in anyway injuring the recording sheet or the stylus assembly.

The stylus assembly'illustrated in Figure, 3 pro- `vides extreme exibility of recording and permits the utilization of a stylus of any Vdesired diameter and thus the printing of very line lines.

Futhermorerit precludes the accumulation of conductive material upon the point of thestylus which wouldV normally Vtend to distort the recorded image. structure of metallic'element iiiV and insulating member 62,.the curvature of theintegral surforation 83 and the metallic cylindrical member Y means of the knurled screwY 84 which threadsV Yinto Vcorresponding threadedperforation 85,

v-Accordlngly this places themetallic stylus at the potential of the metallicsupporting members. This of course requiresthat the drum Y3l be inf sulatedly positioned'upon the supportingVV members. If, on theY other hand, it is desired 'to have thefdrum at .the potential of the supportingv faces 63 and iid is predetermined to meetv the characteristics ofthe drum diameter andthe particular, type of recordingsheet utilized.

The insulatingmaterial 5.2 utilized in constructing the stylus assembly indicated must be Vable to withstand the heating effects of the pasf sage of electrical currents throughv thestylus.

member 'El and mustbe able to Vwithstand the constant wear imposed thereuponlduring the slidfing surface engagement with the record sheet.

'of thefrecording' sheet. -'However, due tothe simpliV ity of the particularstylus 'structure' which I have illustratedin A It is thus preierable 'toutili'zea V material for the insulatingmemb'er 62 whichV will wear mechanically at substantially thesame ratefasthe l metallic element 6 i under the -abrasive induence Figure V3, it is obvious that the stylus Vassembly In the fabrication of the unitary 6l 52 may be disassembled as often as required and the surfaces E53-64 thereof ret-polished to the necessary curvature. The clearance provided at 86 will permit the spring 8! to maintain the necessam7 contact pressure between the stylus surface and the record sheet even though the stylus may be shortened slightly during the polishing. Furthermore the straight end of the stylus 6l will permit numerous repolishings Without the displacement of the point of contact With the record sheet.

It will now be evident that these speciiic disclosures may be modified by those skilled in the art, and thus I prefer to be bound by the scope of the appended claims.

I claim:

1. In a facsimile recorder, a member for carrying a sheet on which a record is to be made, a body of insulating material, a stylus comprising a needle-like conductive element of substantially uniform cross-section throughout its length rigidly embedded in said insulating material against movement with respect ta said insulating material, one end of said stylus being exposed through one end surface of said insulating material, said one end of said insulating material having a convex curvature of relatively large radius compared to the size of said needlelike stylus, the exposed end being flush with Said end surface f said insulating material, said exposed end of the stylus forming with said insulating material a -continuous uniform smooth contacting surface, a housing for said body of insulating material and a spring for biasing said body of insulating material into rm contact with said sheet, said stylus being normal to said sheet at the point of contact therewith, a pivoted arm for supporting said housing, and means for predetermining the position of said pivoted arm.

2. In a facsimile recorder, a member for carrying a sheet on which a record is to be made,` a

body of insulating material, a stylus comprising a needle-like conductive element of substantially uniform cross-section throughout its length rigidly embedded in said insulating material against movement with respect to said insulating material, one end of said stylus being exposed through one end surface of said insulating material, the portion of said stylus near the exposed end being straight and the remaining portion being distorted along its length, said one end of said insulating material having a convex curvature of relatively large radius ycompared to the size of said needle-like stylus, the exposed end being Hush with said end surface of said insulating material, said exposed end of the stylus forming with said insulating material a continuous uniform smooth contacting surface, a housing for said body of insulating material and a spring for biasing said body of insulating material into rm contact with said sheet, said stylus being normal to said sheet at the point of contact therewith, a pivoted arm for supporting said housing, and means for predetermining the position of said pivoted arm.

WILLIAM G. H. FINCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,438,829 Howell Dec. 12, 1922 1,755,793 Peters Apr. 22, 1930 1,915,426 Kohler June 27, 1933 2,003,680 De Forest June 4, 1935 2,026,872 De Forest Jan. 7, 1936 FOREIGN PATENTS Number Country Date 216,983 Switzerland Jan. 16, 1942 

